1. Field of the Invention
The present invention relates to a scroll fluid machine for compressing or expanding or pressure feeding fluid, specifically to a seal configuration of a scroll fluid machine having multistage compression section in which the fluid compressed in the preceding stage compression section is cooled to be compressed in the succeeding stage compression section and a seal element is provided to prevent the leakage of the compressed fluid from the succeeding stage compression section to the preceding stage compression section.
2. Description of the Related Art
It is general in scroll fluid machines that revolving scrolls and stationary scrolls are cooled with cooling air or cooling fluid to remove the heat generated by the compression of the fluid. To attain a compression ratio larger than usual is possible by increasing the number of turns of the scroll. However, there arise problems by increasing the compression ratio than usual that not only the machine becomes large but the life of the bearings and seal elements are shortened due to the high temperature higher than usual owing to the larger compression ratio.
Therefore it becomes necessary to provide a larger cooling device to obtain a larger amount of cold heat for removing the increased heat due to increase compression ratio from the revolving scroll and stationary scroll. In a scroll fluid machine, the fluid is taken in from the peripheral part of the end plate of the revolving scroll, the compression space into which the fluid is taken in is reduced toward the center to compress the fluid, and the compressed fluid is discharged from the discharge port located in the center part. High level technique is necessary to efficiently cool the center part.
For this reason, a multistage compression type scroll machine was demanded which has two stages of compression sections, the compressed fluid discharged from the preceding stage being passed through the cooler to be introduced to the succeeding stage to be again compressed. The multistage compression type scroll machine can compress fluid to a desired high compression ratio without raising the temperature of the constituent parts of the scroll fluid machine higher than usual by restraining the temperature of the compressed fluid in the preceding stage to the temperature the constituent parts allow, cooling the compressed fluid compressed in the preceding stage compression section, and then again compressing the compressed and cooled fluid if the succeeding stage compression section.
A multistage compression type scroll machine which has two stages of compression sections and in which the compressed fluid from the preceding stage is cooled by passing through a cooler and then introduced to the succeeding stage to be again compressed is disclosed in Japanese Unexamined Patent Publication 54-59608.
The conventional art includes, however, the problem as described below. This will be explained with reference to FIG. 10 to 12. The discharge port 2e in the vicinity of the final compression chamber of the preceding stage compression section and the suction port 2f, which communicate with the space into which the fluid is taken in, of the succeeding stage compression section are connected with a piping by the medium of a cooler not shown in the drawing, the connection constituting an intermediate passage.
Now, after the compression space S3 of the preceding stage compression section communicates with the discharge port 2e of the preceding stage compression section, the compression space S6 and T6 of the succeeding stage compression section become communicated with the compression space S5 of the preceding stage compression section, as shown in FIG. 10. The fluid taken into the compression space S6 is compressed by the rotation of the revolving scroll lap 10b to the compression space S8, and the fluid taken into the compression space T6 is compressed to the compression space T8. Therefore, the pressure in the space S8 is higher than that in the space S6, and the pressure in the space T8 is higher than that in the space T6.
As can be seen in FIG. 11(a), FIG. 11(b), and FIG. 12, which show respectively A—A section, B—B section, and C—C section in FIG. 10, a tip seal 53 is received in the groove 41 formed in the tip of the revolving scroll lap 10b and in the groove 40 formed in the tip of the stationary scroll lap 9c respectively. As the tip seal 53 is shaped narrower in width than that of the groove 40 and 41, the tip seals 53, 53 receive the pressure of the compressed fluid of each compression space to be pushed against the mirror face each mating scroll and at the same time to be pushed against the wall each groove toward lower pressure side.
Accordingly, the passage 30 and 31 communicating with the compression space T6 are formed as shown in FIG. 11(a), and the leakage to the lower pressure space T6 is possible.
The passage 32 and 51 communicating with the compression space S8 are formed as shown in FIG. 11(b), and the leakage to the lower pressure space S6 is possible.
The tip seal is pushed against the groove wall toward lower pressure side. However, the side face of the tip seal and the groove face can not be brought to absolute contact with each other because of the imperfect flatness of the faces. Accordingly, the leakage of high pressure fluid in the direction of arrow 76 to the gap 80 between the tip seal 14 and 53 is possible as shown in FIG. 12(a) which shows C—C section in FIG. 10.
There is a gap between the bottom of the groove formed in the tip of the revolving scroll lap and the tip seal 53, so the leakage of the fluid is possible from higher pressure side to lower pressure side. This means that, as a gap exists between the end face 41a of the groove 41 and the end face 53a of the tip seal 53 at the end part 10d of the revolving scroll lap 53, the leakage of the compressed fluid in the direction of arrow 78 is possible, and also the leakage as shown by arrow 77 is possible from the passage 51.
Therefore, as shown in FIG. 10 and FIG. 12(a), the high pressure fluid leaks from the succeeding stage compression section to the preceding stage compression section through the gap 80 shown by arrow 29 and 76 to be taken into the preceding stage compression section to be compressed again, which causes problems of high temperature and excessive power requirement for compression.